I hated 4.0, so I reinstalled 3.6 and it won't open. What do I do now?

Question

I uninstalled 4.0 and reinstalled 3.6 using there instructions from your forum...
If you still want to downgrade to Firefox 3.6.* you can uninstall Firefox 4, but do not select the option to "Remove my Firefox personal data". If you select that option it will delete your bookmarks, passwords and other user data.
You can then install Firefox 3.6.* available from http://www.mozilla.com/en-US/firefox/all-older.html - it will automatically use your current bookmarks, passwords etc.
To avoid possible problems with downgrading, I recommend going to your profile folder and deleting the following files if they exist - extensions.cache, extensions.rdf, extensions.ini, extensions.sqlite and localstore.rdf. Deleting these files will force Firefox to rebuild the list of installed extensions, checking their compatibility, and reset toolbar customizations.
For details of how to find your profile folder see https://support.mozilla.com/kb/Profile
The reinstall of 3.6 won't open. What do I do now???

Answer 1

The directions you posted look good to me, though I would not have deleted the files, there is no harm, Firefox will recreate them.
I expect that you have an extension that is bad probably one bad enough to be listed in
* [http://kb.mozillazine.org/Problematic_extensions Problematic extensions - MozillaZine Knowledge Base]
or listed in the blocklist
* [https://www.mozilla.com/blocklist/ Add-ons Blocklist | Mozilla]
I would suggest going back to Firefox 4.0.1 and trying to fix your problems there. In either case you will need to open in Firefox Safe Mode, see [http://kb.mozillazine.org/Safe_Mode Safe Mode - MozillaZine Knowledge Base] which will disable extensions and I would expect that you would be able to run Firefox that way. If you can run okay only in Safe Mode then that almost certain means an extension problem.
If you can use menus but not use "Enter" on the location bar that proably points to
"AVG Safe Search" extension and you would have to follow directions in Problematic extensions to reinstall AVG Free without the Link Scanner Component. If you can't easily identify the extension causing problems then see
* Extension issues in [http://kb.mozillazine.org/Standard_diagnostic_(Firefox)#Extension_issues Standard diagnostic - Firefox - MozillaZine Knowledge Base]
Firefox 4.0 is not a problem you thought it was, since you can customize the appearance.
You can make Firefox 4.0.1 look like Firefox 3.6.17, see numbered items 1-10 in the following topic [http://dmcritchie.mvps.org/firefox/firefox-
problems.htm#fx4interface Fix Firefox 4.0 toolbar user interface, problems (Make Firefox 4.0 look like 3.6)]